BT is to argue its £12.5bn takeover of EE in front of competition watchdogs this week with a formal submission to the Competition and Markets Authority (CMA).
Sky, TalkTalk and Vodafone have all expressed concerns over the sale which would further boost BT's financial powers with EE's deal to share mobile mast infrastructure with Three, through MBNL, a major bone of contention.
Rivals are expected to argue that BT must sell off parts of its mobile spectrum as, when combined with EE, its holdings would breach a cap imposed by Ofcom. However, from next year, new spectrum rights will mean BT's share of the airwaves would fall under the cap.
Reports suggest BT may agree with the CMA to sell a some of its airwaves in anticipation of acquiring more 800MHz airwaves, the lowest 4G frequency, when regulators turn their eye to Three and O2's proposed merger.
The telecoms provider is expected to claim that the deal will ultimately benefit consumers pointing to European counterparts who have lowered prices by bundling mobile with broadband, landline and subscription TV.
Regulatory scrutiny of the BT/EE deal is expected to take many months.